Method and apparatus for writing servo information on a recording medium

ABSTRACT

A servo system for writing servo information on a recording medium of a hard disk drive and for determining head position based on the servo information with a tracking accuracy, the servo system including a first magnetic head and a servo writer. The servo writer is configured to write the servo information on the recording medium by forming, using the first magnetic head, a first servo pattern comprising a servo burst pattern on a segment of a first track of a first layer of the recording medium; and by forming a second servo pattern comprising addressing information on a segment of a second track of a second layer of the recording medium. The second track is arranged half a width of the first track from the first track to increase the tracking accuracy of the servo system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/378,778 (now U.S. Pat. No. 9,111,562), filed Aug. 14, 2014, which isa 371 of International Application No. PCT/SG2013/000065, filed Feb. 18,2013, which claims the benefit of priority of Singapore PatentApplication No. 201201136-7, filed 17 Feb. 2012. The entire disclosuresof the above applications are incorporated herein by reference.

FIELD

Various aspects of this disclosure relate to recording media and methodsof writing servo information on the same.

BACKGROUND

In conventional hard disks having a rotating magnetic medium, there isonly one magnetic layer to record data. As such, the servo patterninformation is recorded in servo wedges. This way of storing servoinformation is also known as embedded servo. FIG. 1 is a schematic 100showing the arrangement of servo pattern information 102 along a trackon the magnetic layer. Servo information 102 is interspersed with datainformation 104.

The position of the read/write head is demodulated from the servowedges. Thus, the sampling frequency of the servo control system is thuslimited by the number of servo wedges in one revolution, and therotating speed of disk. To improve the servo performance, such astracking accuracy for high track density drive, a higher sampling rateis needed, which in turn requires more servo wedges to be placed in themagnetic layer. However, this will cause less data sector to beavailable for recording the user data. This is undesirable.

SUMMARY

In various embodiments, a method of writing servo information to arecording medium may be provided. The method include forming a firstservo pattern (including a servo burst pattern) on a segment of a firsttrack of a first layer of the recording medium, the first track having atrack width. The method may further include forming a second servopattern (including addressing information) on a segment of a secondtrack of a second layer of the recording medium. The second track isarranged from the first track by half the track width.

In various embodiments, a recording medium may be provided. Therecording medium may include a first servo pattern including a servoburst pattern on a segment of a first track of a first layer of therecording medium. The method may further include a second servo patternincluding addressing information on a segment of a second track of asecond layer of the recording medium. The second track may be arrangedfrom the first track by half the track width.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be better understood with reference to the detaileddescription when considered in conjunction with the non-limitingexamples and the accompanying drawings, in which:

FIG. 1 shows the arrangement of servo pattern information along a trackon the magnetic layer.

FIG. 2 shows a top planar view of a recording medium.

FIG. 3A shows the cross sectional side view of a portion of a datarecording medium along a plane parallel to the circumference of the datarecording medium according to various embodiments; FIG. 3B shows thecross-sectional side view across three data tracks and two servo tracksaccording to various embodiments; FIG. 3C shows the top view of a datatrack and two servo tracks according to various embodiments; and FIG. 3Dshows types of address information according to various embodiments.

FIG. 4 shows a method of writing servo information according to variousembodiments on a recording medium.

FIG. 5A shows a cross sectional side view of a data recording mediumalong a plane parallel to the circumference of the data recording mediumwith servo information stored according to various embodiments; FIG. 5Bshows the cross-sectional side view across a data track and a servotrack with servo information stored according to various embodiments;and FIG. 5C shows the top view of a data track and a servo track withservo information stored according to various embodiments.

FIG. 6 shows the top view of portions of data tracks and two servotracks with servo information stored according to various embodiments.

FIG. 7 shows the side view of portion along a servo track in the firstlayer and a data track along the second layer with data and servoinformation stored according to various embodiments.

FIG. 8, which include 8A to G, shows a method to arrange the servoinformation shown in FIG. 7 according to various embodiments; whereinFIG. 8A shows a top view of servo tracks in a first layer after awriting pass according to various embodiments; wherein FIG. 8B shows theside view of a portion along a servo track in the first layer and theoverlying second layer after a writing pass according to variousembodiments; wherein FIG. 8C shows the cross section of the first trackon the first layer as well as overlying tracks and on the second layer;wherein FIG. 8D shows a wide head according to various embodiments;wherein FIG. 8E shows a wide head in operation according to variousembodiments; wherein FIG. 8F shows a top view of servo tracks a firstlayer as well as portions of data tracks in a second layer after asubsequent writing pass according to various embodiments; and whereinFIG. 8G shows the side view of a portion along a servo track in thefirst layer and the overlying second layer after a subsequent writingpass according to various embodiments.

FIG. 9A shows a signal map of a conventional single layer recordingmedium; FIG. 9B shows another signal map of a conventional single layerrecording medium; FIG. 9C shows a signal map of a multi-layer recordingmedium according to various embodiments; FIG. 9D shows the signal map ofthe multi-layer recording medium after a writing pass is carried outaccording to various embodiments; FIG. 9E shows the signal map of themulti-layer recording medium after a subsequent writing pass is carriedout according to various embodiments.

FIG. 10 shows the side view of portion along a servo track in the firstlayer and a data track along the second layer with data and servoinformation stored according to various embodiments.

FIG. 11, which includes FIGS. 11A to H, shows a method to arrange theservo information shown in FIG. 10 according to various embodiments;wherein FIG. 11A shows a top view of portions of a plurality of tracksconfigured to store servo information after a first step; wherein FIG.11B shows a side view of FIG. 11A; wherein FIG. 11C shows a top view ofportions of a plurality of tracks configured to store servo informationafter a second step; wherein FIG. 11D shows a side view of FIG. 11C;wherein FIG. 11E shows a top view of portions of a plurality of tracksconfigured to store servo information after a third step; wherein FIG.11F shows a side view of FIG. 11E; wherein FIG. 11G shows a top view ofportions of a plurality of tracks configured to store servo informationafter a fourth step; and wherein FIG. 11H shows a side view of FIG. 11G.

FIG. 12 shows the signal map of a multi-layer recording medium after awriting pass is carried out according to various embodiments.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practiced.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration”. Any embodiment or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs.

The word “over” used with regards to a deposited material formed “over”a side or surface, may be used herein to mean that the depositedmaterial may be formed “directly on”, e.g. in direct contact with, theimplied side or surface. The word “over” used with regards to adeposited material formed “over” a side or surface, may be used hereinto mean that the deposited material may be formed “indirectly on” theimplied side or surface with one or more additional layers beingarranged between the implied side or surface and the deposited material.

The product can be a consumer electronic device which can be operable invarious orientations, and thus it should be understood that the terms“top”, “bottom”, “base”, “down”, “sideways”, “downwards” etc., when usedin the following description are used for convenience and to aidunderstanding of relative positions or directions, and not intended tolimit the orientation of the recording medium or the productincorporating the recording medium.

Various aspects may provide a recording medium and a method of writingservo information on the same that is able to address at least partiallythe abovementioned challenges.

FIG. 2 is a schematic 200 showing a top planar view of a recordingmedium. The recording medium may have tracks 202 running in parallel tothe circumference of the recording medium. The recording medium may alsobe divided into data sectors 204 with addressing information (eg.GrayCode 206 and other addressing information 208) interspersed betweenthe data sectors.

In various embodiments, the recording medium may be in the shape of adisk. The disc may have a first main surface and a second main surfacesubstantially parallel to the first main surface. The disc may also havea lateral side joining the first main surface and the second mainsurface. The lateral side may be substantially perpendicular to thefirst main surface and the second main surface.

The medium may be a magnetic medium. The first layer or servo layer maybe a magnetic layer or more specifically a ferromagnetic layer. Thesecond layer or data recording layer (alternatively called the datalayer) may be a magnetic layer or more specifically a ferromagneticlayer. The first magnetic layer and the second magnetic layer may form asingle monolithic structure. Further, the first magnetic layer and thesecond magnetic layer may be put on the same side of a disk platter andthey may be read and/or processed together.

In other words, a magnetic medium including two layers may be providedto store information. One of the layer is stacked on top of the otherlayer. The second layer (which may alternatively be called the datarecording layer) may be configured to store user data. References to“data” usually refer to “user data”, unless it is otherwise clear fromthe context. A portion of the servo information is stored in the firstlayer (which may alternatively be called the servo layer).

FIG. 3A is a schematic 300 a showing the cross sectional side view of aportion of a data recording medium along a plane parallel to thecircumference of the data recording medium according to variousembodiments. In various embodiments, the recording medium may includetwo layers, i.e. a first layer 302 and a second layer 304. One layer maybe stacked over another layer to form the disk (i.e. the two layers forma stacked arrangement). In various embodiments, the second layer 304 maybe arranged over the first layer 302. In various embodiments, the firstlayer 302 may be configured to record at least a portion of servopattern information and is called the servo layer. In variousembodiments, the second layer 304 may be configured to record data andis called the data recording layer (or data layer). The second layer 304may be further configured to record addressing information of servopattern information. The first layer 302 may be separated from thesecond layer 304 by one or more intermediate layers 306. Alternatively,the second layer 304 may be on the first layer 302.

The recording medium may have a plurality of tracks. The plurality oftracks (for instance, a first track and a second track) may run parallelto the circumference of the recording medium. As such, the first trackmay be parallel to the second track. The plurality of tracks may form aplurality of concentric rings on the recording medium. The plurality ofconcentric rings have a common centre coinciding with an axis of thedisk running from the center of the first main surface of the disk tothe second main surface of the disk. In operation, the recording mediummay be rotated about the axis of the disk. Each track may include aplurality of segments along the length of the track.

FIG. 3B is a schematic 300 b showing the cross-sectional side viewacross three data tracks 304 a, 304 b, 3404 c and two servo tracks 302a, 302 b according to various embodiments. FIG. 3B may correspond to theview in a direction indicated by arrow 308 in FIG. 3A. The data tracks304 a, 304 b, 304 c may be configured to record data. The data tracks304 a, 304 b, 304 c may be further configured to record addressinginformation of servo pattern information. The second layer or data layer304 may include the data tracks 304 a, 304 b, 304 c. The servo tracks302 a, 302 b may be configured to record at least a portion of servoinformation. For instance, the servo tracks 302 a, 302 b may beconfigured to record servo bursts. The first layer or servo layer 302may include the servo tracks 302 a, 302 b. A reader head 310 may bepositioned over the tracks.

FIG. 3C is a schematic 300 c showing the top view of a data track 304 band two servo tracks 302 a, 302 b according to various embodiments. FIG.3C may correspond to the view indicated by arrow 312 in FIG. 3A.

In various embodiments, servo information may include a first servopattern. The first servo pattern may include a servo burst pattern.Servo information may also include a second servo pattern. The secondservo pattern may include addressing information. In variousembodiments, the first servo pattern may be stored in the first layer orservo layer 302. The second servo pattern (including addressinginformation) may be stored in the second layer or data recording layer304. Additionally, data may be stored in the second layer or data layer304. In various embodiments, storing the first servo pattern in theservo layer 302 may free up space in the data recording layer 304 andmay improve surface utilization rate for the data recording layer 304.

FIG. 3D is a schematic 300 d showing the types of address informationaccording to various embodiments. Addressing information may includeautomatic gain control (AGC) 314. Additionally, addressing informationmay include sector address mark (SAM) 316. Addressing information mayalso include GrayCode 318. AGC 314 may occupy 80 bits, while SAM 316 mayoccupy 12 bits and GrayCode 318 may occupy 24 bits.

FIG. 4 is a schematic 400 that shows a method of writing servoinformation according to various embodiments on a recording medium. Themethod may provide, in 402, forming a first servo pattern (including aservo burst pattern) on a segment of a first track of a first layer ofthe recording medium, the first track having a track width. The methodmay further provide, in 404, forming a second servo pattern (includingaddressing information) on a segment of a second track of a second layerof the recording medium. The second track may be arranged from the firsttrack by half the track width.

In various embodiments, the first track may be servo track 302 a asshown in FIGS. 3B and 3C the second track may be data track 304 b asshown in FIGS. 3B and 3C. The first track may have a track width. Thesecond track may also have a track width, which may be substantiallyequal to the track width of the first track. In fact, in variousembodiments, the track width of each track in the recording medium,including each servo track and each data track, may be substantiallyequal to one another.

The second track 304 b may be arranged from the first track 302 a byhalf a track width. In other words, the second track 304 b may bearranged from the first track 302 a such that the projection of thesecond track 304 b on a plane parallel to the first main surface of therecording medium (or the second main surface of the recording medium) ishalf a track width from the projection of the first track 302 a on theplane.

FIG. 5A is a schematic 500 a showing a cross sectional side view of adata recording medium along a plane parallel to the circumference of thedata recording medium with servo information stored according to variousembodiments. The recording medium may include a first layer 502 and asecond layer 504 on the first layer 502. FIG. 5B is a schematic 500 bshowing the cross-sectional side view across a data track 504 b and aservo track 502 a with servo information stored according to variousembodiments. FIG. 5B may correspond to the view in a direction indicatedby arrow 508 in FIG. 5A. FIG. 5C is a schematic 500 c showing the topview of a data track 504 b and a servo track 502 a with servoinformation stored according to various embodiments. FIG. 5C maycorrespond to the view indicated by arrow 512 in FIG. 5A.

In various embodiments, a recording medium may be provided. Therecording medium may include a first servo pattern 514 (including aservo burst pattern) on a segment of a first track 502 a of a firstlayer 502 of the recording medium. The recording medium may also includea second servo pattern 516 (including addressing information) on asegment of a second track 504 b of a second layer 504 of the recordingmedium. The second track 504 b may be arranged from the first track 502a by half the track width.

In other words, servo information may be arranged on the recordingmedium such that a first portion of the servo information (i.e. thefirst servo pattern 514 including a servo burst pattern) is on a firstlayer 502. A second portion of the servo information (i.e. a secondservo pattern 516 including addressing information) is on a second layer504. The first servo pattern 514 may be stored on a segment of the firsttrack 502 a located in the first layer 502 of the recording medium. Thesecond servo pattern 516 may be stored on a segment of the second track504 b located in the second layer 504 of the recording medium. Theprojection of the first track 502 a on a plane parallel to the firstmain surface (or second main surface) of the recording medium may behalf a track width from the projection of the second track 504 b on theplane.

In order to demodulate the addressing information in real time, theaddressing information may be required to be of a good quality. As thesecond layer (data recording layer) is positioned closer to a reader (orread head) during reading, it may be desirable for addressinginformation to be stored in the second layer (data recording layer). Theaddressing information may include automatic gain control (AGC).Additionally, addressing information may include sector address mark(SAM). Addressing information may also include GrayCode.

According to various embodiments, the automatic gain control (AGC) mayalso be used to establish a feedback clock signal for synchronization ofmedia read and write operations to minimize the effect of spindle speedfluctuation. The AGC may also be used to normalize the amplitude ofread-back signal for gray code detector and SAM detector. The SAM mayprovide the down-track information which tells the number of servosectors that read head has crossed. The GrayCode may indicate the servotrack number (track address) that read head is following. All servosectors on a servo track have the same servo track number encoded.

The number of track address markings may be reduced to 100 while stillmaintaining performance of the track seeking process. While theaddressing information such as the GrayCode is stored in the secondlayer (data recording layer), the total area of the data area forstoring servo information may still less than 2%. As such, by storingthe servo bursts in the first layer (servo layer) and storing theaddressing information in the second layer (first layer), large amountof area may be devoted for storing data without reducing performance.

FIG. 6 is a schematic 600 showing the top view of a data track 604 b,portions of data tracks 604 a, 604 c and two servo tracks 602 a, 602 bwith servo information stored according to various embodiments. Onlyportions of the data tracks 604 a, 604 c having servo information 616 a,616 c, 616 d, 616 f are shown. The remaining portions of the data tracks604 a, 604 c are indicated by dashed lines. The second layer (includingdata tracks 604 a, 604 b, 604 c) may be arranged over the first layer(including servo tracks 602 a, 602 b).

The recording medium may include a first servo pattern 614 a, 614 c(including a servo burst pattern) on a segment of a first track 602 a ofa first layer of the recording medium. The recording medium may alsoinclude a second servo pattern 616 b, 616 e (including addressinginformation) on a segment of a second track 604 b of a second layer ofthe recording medium. The recording medium may further include a thirdservo pattern 614 b, 614 d including a subsequent servo burst pattern ona segment of a third track 602 b of the first layer of the recordingmedium. The third track 602 b may be arranged from the second track 604b by half a track width.

The second track 604 b may be between the first track 602 a and thethird track 602 b. “Between” may mean that the projection of the centerline of the second track 604 b on a plane parallel to the first mainsurface (or second main surface) of the recording medium is between theprojection of the center line of the first track 602 a on the plane andthe projection of the center line of the third track 602 b on the plane.The center line of a track runs along the track.

In various embodiments, the servo burst pattern may be of a firstfrequency (II) and the subsequent servo burst pattern may be of a secondfrequency (f2). The servo burst patterns provide dual frequency signalsto a read head. A positioning error signal (PES) may generated byfinding the difference in signal amplitude between f1 and f2. When aread head is positioned over the edge between the first track 602 a andthe third track 602 b (i.e. over the entire width of the second track604 b), PES may be at a minimum. The read head may ideally be positionedover the edge during reading for good track following.

In various embodiments, the servo burst pattern may be of a singlefrequency or of multi-frequencies. For instance, the servo burst patternmay also be of triple frequencies. In various embodiments, the servoburst pattern and the subsequent servo burst pattern may be of onefrequency. The servo burst pattern and the subsequent servo burstpattern may be direct current (DC).

FIG. 7 is a schematic 700 showing the side view of portion along a servotrack in the first layer 702 and a data track along the second layer 704with data and servo information stored according to various embodiments.FIG. 7 shows a recording medium including a first servo pattern 714(including a servo burst pattern) on a segment of a first track of afirst layer 702 of the recording medium according to variousembodiments. FIG. 7 further shows a second servo pattern 716 (includingaddressing information) on a segment of a second track of a second layer704 of the recording medium according to various embodiments. The secondtrack may be arranged from the first track by half the track width. Theaddressing information may include auto gain control (AGC), sectoraddress mark (SAM) and GrayCode.

The portion of the second layer (data recording layer) 718 correspondingto the first servo pattern 714 in the first layer may be configured tostore data.

The portion of the first layer (servo layer) 720 corresponding to thesecond servo pattern 716 in the second layer may be configured to beleft unused.

In various embodiments, a portion of the second layer corresponding to asegment of the first layer means portions of the data track(s) adjacentto the segment of the first layer or portions of the data track(s)separated from the segment of the first layer by one or moreintermediate layers within the recording medium. Conversely, a portionof the first layer corresponding to a segment of the second layer meansportions of the servo track(s) adjacent to the segment of the secondlayer or portions of the servo track(s) separated from the segment ofthe second layer by one or more intermediate layers within the recordingmedium. The projection of the segment of the first layer on a planeparallel to the first main surface (or second main surface) of therecording medium may overlap entirely or substantially with theprojection of the corresponding portion of the second layer on theplane. Conversely, the projection of the segment of the second layer ona plane parallel to the first main surface (or second main surface) ofthe recording medium may overlap entirely or substantially with theprojection of the corresponding portion of the first layer on the plane.In various embodiments wherein the second layer is on or over the firstlayer, the corresponding portion of the second layer to a segment on thefirst layer may directly on or above the segment on the first layer.Additionally, the corresponding portion of the first layer to a segmenton the second layer may be directly below the segment on the secondlayer.

In various embodiments, the method may include using shingled writingscheme. The method may include forming the servo information in awriting pass, followed by rewriting some of the servo information in asubsequent writing pass.

FIG. 8A to G illustrate a method to arrange the servo information shownin FIG. 7 according to various embodiments. FIG. 8A is a schematic 800 ashowing the top view of servo tracks 802 a, 802 b, 802 c, 802 d in afirst layer 802 after a writing pass according to various embodiments.FIG. 8B is a schematic 800 b showing the side view of a portion along aservo track 802 a in the first layer 802 and the overlying second layer804 after a writing pass according to various embodiments. FIG. 8B maycorrespond to the view in a direction indicated by arrow 812 in FIG. 8A.

In various embodiments, the method may include forming an intermediateservo pattern 816 a (including the addressing information) on asubsequent segment of the first track 802 a of the first layer 802 ofthe recording medium. In other words, the method may include forming theintermediate servo pattern 816 a on an adjacent segment on the samelayer and on the same track when forming the first servo pattern 814 a.

In various embodiments, forming the first servo pattern 814 a (includingthe servo burst pattern) on the segment of the first track 802 a of thefirst layer 802 of the recording medium may be carried out during awriting pass of a magnetic head. Forming the intermediate servo pattern816 a (including the addressing information) on the subsequent segmentof the first track 802 a of the first layer 802 of the recording mediummay be carried out during the same writing pass of the magnetic head. Inother words, the intermediate servo pattern 816 a may be formed togetherwith the first servo pattern 814 a on a writing pass.

In various embodiments, the first servo pattern 814 a (including theservo burst pattern) on the segment of the first track 802 a of thefirst layer 802 of the recording medium may also be formed on theportion of the second layer 804 corresponding to the first servo pattern814 a on the segment of the first track 802 a of the first layer 802.The first servo pattern 814 a on the segment of the first track 802 a ofthe first layer 802 of the recording medium may also be formed on atleast a part of a segment of the second track 804 a of the second layer804 of the recording medium. The part of the segment may include abouthalf of the second track 804 a directly on or above the segment of thefirst track 802 a of the first layer 802 of the recording medium. Thefirst servo pattern 814 a on the segment of the first track 802 a of thefirst layer 802 of the recording medium may also be formed on at least apart of a segment of the track 804 e of the second layer 804 of therecording medium. The part of the segment may also include about halfthe track 804 e directly on or above the segment of the first track 802a of the first layer 802 of the recording medium.

FIG. 8C shows a schematic 800 c showing the cross section of the firsttrack 802 a on the first layer as well as overlying tracks 804 a and 804e on the second layer 804. FIG. 8C may corresponds to FIG. 8B whenviewed in the direction indicated by arrow 808 in FIG. 8B. In variousembodiments, the intermediate servo pattern 816 a (including theaddressing information) may be formed on the portion 830 of the secondlayer 804 corresponding to the intermediate servo pattern 816 on thefirst track 802 a of the first layer 802. The intermediate servo pattern816 a formed on the subsequent segment of the first track 802 a of thefirst layer 802 of the recording medium may also be formed on at least apart of a segment 830 a of the second track 804 a of the second layer804 of the recording medium. The part of the segment 830 a may includeabout half of the second track 804 a directly on or above the segment ofthe first track 802 a of the first layer 802 of the recording medium.The first servo pattern 814 a on the segment of the first track 802 a ofthe first layer 802 of the recording medium may also be formed on atleast a part of a segment 830 b of the track 804 e of the second layer804 of the recording medium. The part of the segment 830 b may alsoinclude about half the track 804 e directly on or above the segment ofthe first track 802 a of the first layer 802 of the recording medium.

The first servo pattern 814 a and the intermediate servo pattern 816 aon the second layer may not be necessary. The first servo pattern 814 amay be replaced during the subsequent writing pass. The intermediateservo pattern 816 a may be replaced by the user data in the datarecording.

In various embodiments, the magnetic head may write an intermediateservo pattern 816 a (including addressing information AGSCO) and thefirst servo pattern 814 a (including servo burst of a first frequencyf1) in the first track 802 a. The magnetic head may then move one trackwidth to write a subsequent intermediate servo pattern 816 b (includingaddressing information AGSC1) and the third servo pattern 814 b(including subsequent servo burst of a second frequency f2) in the thirdtrack 802 b. The magnetic head may then repeat the previous steps bymoving to subsequent servo tracks (such as 802 c, 802 d etc.) to writethe subsequent intermediate servo patterns such as 816 c, 816 d(including addressing information AGSC2, AGSC3 etc.) and servo patternssuch as 814 c and 814 d (including subsequent servo bursts).

In various embodiments, the magnetic head may be a wide head. FIG. 8D isa schematic 800 d showing a wide head 822 according to variousembodiments. FIG. 8E is a schematic 800 e showing the wide head 822 inoperation according to various embodiments. The wide head may have awidth w and a length p. The width w may be more than 300 nm. The widehead 822 may be wide enough to provide enough magnetic field to saturatethe servo layer 802 for writing servo information.

The wide head 822 may be configured to confine the magnetic field suchthat prior information that has been written on preceding tracks are notoverwritten. The wide head 822 may, for instance, have a shieldingcomponent to shield the magnetic field to confine the magnetic field.The wide head 822 may write one track at a time.

For each of the servo track, the addressing information (including theAGC, the SAM and the GrayCode) may be written in one go of a full trackwriting. The wide head 822 may be used to write the intermediate servopattern 816 a (including addressing information) and the first servopattern 814 a (including servo burst of a first frequency f1) in thefirst track 802 a. The wide head 822 may then move by one track widthand writes the subsequent intermediate servo pattern 816 b (includingaddressing information) and the third servo pattern 814 b (includingsubsequent servo burst of a second frequency f2) in the third track.This may be repeated until the wide head 822 has completed writing theservo information over the entire recording medium.

FIG. 8F is a schematic 800 f showing the top view of servo tracks 802 a,802 b, 802 c, 802 d in a first layer 802 as well as portions of datatracks 804 a, 804 b, 804 c in a second layer 804 after a subsequentwriting pass according to various embodiments. FIG. 8G is a schematic800 g showing the side view of a portion along a servo track 802 a inthe first layer 802 and the overlying second layer 804 after asubsequent writing pass according to various embodiments. FIG. 8G maycorrespond to the view in a direction indicated by arrow 824 in FIG. 8G.

In various embodiments, forming the second servo pattern 820 a(including addressing information) on a segment of the second track 804a of the second layer 804 of the recording medium may be carried outduring a subsequent writing pass of a subsequent magnetic head. Thesubsequent writing pass may be conducted at drive level during driveself-test.

In various embodiments, the intermediate servo pattern 816 a formed onthe subsequent segment of the first track 802 a of the first layer 802of the recording medium during the first pass may be used as a referencewhen forming the second servo pattern 820 a on the segment of the secondtrack 804 a of the second layer 804 during the second pass. Similarly,the subsequent intermediate servo patterns such as 816 b, 816 c formedon respective subsequent segments of the subsequent first tracks such as802 b, 802 c etc. of the first layer 802 of the recording medium duringthe first pass may be used as a reference when forming the subsequentsecond servo patterns such as 820 b, 820 c on respective segments of thesubsequent second tracks such as 804 b, 804 c etc. of the second layer804 during the second pass. In others words, the addressing informationwritten on the recording medium during the initial writing pass may beused as a reference when writing the addressing information during thesubsequent writing pass.

In various embodiments, the subsequent intermediate servo pattern 816 bformed on the subsequent segment of the third track 802 b of the firstlayer 802 of the recording medium during the first pass may be used as areference when forming the second servo pattern 820 a on the segment ofthe second track 804 a of the second layer 804 during the second pass.In various embodiments, both the intermediate servo pattern 816 a andthe subsequent intermediate servo pattern 816 b may be used as areference when forming the second servo pattern 820 a.

The subsequent magnetic head may be a product head.

In various embodiments, the intermediate servo pattern 816 a formed onthe subsequent segment of the first track 802 a of the first layer 802of the recording medium during the first pass may be distorted whenforming the second servo pattern 820 a on the segment of the secondtrack 804 a of the second layer 804 during the second pass. Similarly,the subsequent intermediate servo patterns such as 816 b, 816 c formedon the respective subsequent segments of the subsequent first trackssuch as 802 b, 802 c, 802 d etc. of the first layer 802 of the recordingmedium during the first pass may be distorted when forming the secondservo pattern such as 820 b, 820 c on the respective segments of thesubsequent second tracks 804 b, 804 c etc. of the second layer 804during the second pass.

In other words, the addressing information written during the initialwriting pass may be distorted. There may be residual patterns or nopatterns in the subsequent segment of tracks such as 802 a, 802 b, 802c, 802 d etc. of the first layer 802 of the recording medium after thesecond writing pass. The subsequent segment may be configured to beunused over the lifetime of the recording medium.

In various embodiments, the subsequent intermediate servo pattern 816 bformed on the subsequent segment of the third track 802 b of the firstlayer 802 of the recording medium during the first pass may be distortedwhen forming the second servo pattern 820 a on the segment of the secondtrack 804 a of the second layer 804 during the second pass.

In various embodiments, the first servo pattern 814 a, 814 b etc.(including the servo bursts) on the segment of the first track 802 a,802 b etc. of the first layer 814 of the recording medium may remainover the lifetime of the recording medium.

In various embodiments, additional servo patterns may be formed duringthe writing pass or subsequent writing pass on the correspondingsegments of the second track 804 a, 804 b, 804 c etc. of the secondlayer 804 to first servo patterns 814 a, 814 b etc. The correspondingsegments may be overwritten with data 818 during self-test phase or theactual user data recording.

Various embodiments provide a recording medium wherein the number ofsteps required may be double or more than double the number of servotracks. Various embodiments may provide a method in which half of thenumber of steps for writing servo information is transferred to thedrive level during the subsequent writing pass. Various embodiments mayprovide a method with low manufacturing costs as writing during theinitial writing pass (at disk media level) may be more expensive thanthe subsequent writing pass (at drive level).

FIG. 9A is an image 900 a showing the signal map of a conventionalsingle layer recording medium. Red spots 902 may represent one logicstate while blue spots 904 may represent another logic state. FIG. 9B isanother image 900 b showing the signal map of a conventional singlelayer recording medium. Red spots 906 may represent one logic statewhile blue spots 908 may represent another logic state. FIG. 9C is animage 900 c showing the signal map of a multi-layer recording mediumaccording to various embodiments. Red spots 910 may represent one logicstate while blue spots 912 may represent another logic state. The region914 may be a portion in which the addressing information is stored whilethe region 916 may be a portion in which the servo bursts is stored.FIGS. 9D and 9E show the signals maps obtained from a multi-layerrecording medium in which servo information is written according to amethod illustrated in FIGS. 8A to F according to various embodiments.FIG. 9D is an image 900 d showing the signal map of the multi-layerrecording medium after a writing pass is carried out according tovarious embodiments. Image 900 d shows that the addressing information918 are aligned to the servo bursts 920 in the servo tracks 922. FIG. 9Eis an image 900 e showing the signal map of the multi-layer recordingmedium after a subsequent writing pass is carried out according tovarious embodiments. Image 900 e shows that the addressing information924 in the data tracks 926 are aligned by half a track width from theservo bursts 928 in the servo tracks 930.

FIG. 10 is a schematic 1000 showing the side view of portion along aservo track in the first layer 1002 and a data track along the secondlayer 1004 with data and servo information stored according to variousembodiments. FIG. 10 shows a recording medium including a first servopattern 1014 (including a servo burst pattern) on a segment of a firsttrack of a first layer of the recording medium according to variousembodiments. FIG. 10 further shows a second servo pattern 1016 includingaddressing information on a segment of a second track of a second layer1004 of the recording medium according to various embodiments. The datarecording medium may further include a second servo pattern 1020(including addressing information) on a portion of the first layer 1002,the portion corresponding to the segment (for storing second servopattern 1016) of the second track of the second layer 1004. In otherwords, a portion of the first layer 1002 corresponding to servo pattern1016 may be configured to store a second servo pattern 1020 (includingaddressing information). The addressing information may include autogain control (AGC), sector address mark (SAM) and GrayCode.

The portion of the second layer (data recording layer) 1018corresponding to the first servo pattern 1014 in the first layer may beconfigured to store data.

In various embodiments, the second layer 1004 may be over the firstlayer 1002. The second servo pattern 1020 (including addressinginformation) maybe on a portion of the first layer 1002, the portion ofthe first layer 1002 below the segment of the second track of the secondlayer 1004 (for storing the second servo pattern 1016). In variousembodiments, the second servo pattern 1020 may be on a portion of thefirst layer 1002, the portion of the first layer 1002 corresponding tothe segment of the second track of the second layer 1004.

In various embodiments, a portion of the second layer corresponding to asegment of the first layer means portions of the data track(s) adjacentto the segment of the first layer or portions of the data track(s)separated from the segment of the first layer by one or moreintermediate layers within the recording medium. Conversely, a portionof the first layer corresponding to a segment of the second layer meansportions of the servo track(s) adjacent to the segment of the secondlayer or portions of the servo track(s) separated from the segment ofthe second layer by one or more intermediate layers within the recordingmedium. The projection of the segment of the first layer on a planeparallel to the first main surface (or second main surface) of therecording medium may overlap entirely or substantially with theprojection of the corresponding portion of the second layer on theplane. Conversely, the projection of the segment of the second layer ona plane parallel to the first main surface (or second main surface) ofthe recording medium may overlap entirely or substantially with theprojection of the corresponding portion of the first layer on the plane.In various embodiments wherein the second layer is on or over the firstlayer, the corresponding portion of the second layer to a segment on thefirst layer may directly on or above the segment on the first layer.Additionally, the corresponding portion of the first layer to a segmenton the second layer may be directly below the segment on the secondlayer.

FIGS. 11A to H illustrate a method to arrange the servo informationshown in FIG. 10 according to various embodiments. FIG. 11A is aschematic 1100 a showing a top view of portions of a plurality of tracksconfigured to store servo information after a first step. FIG. 11B is aschematic 1100 b showing a side view of FIG. 11A when viewed from thedirection indicated by 1112 a in FIG. 11A. FIG. 11A shows that the firststep includes writing a first servo pattern 1114 a including servobursts to a segment along a first track 1102 a in the first layer 1102.The servo bursts may be of a first frequency. The first servo pattern1114 a may also be written to a portion of the second layer 1104corresponding to the first servo pattern 1114 a in the first layer 1102.The portion of the second layer 1104 corresponding to the first servopattern 1114 a in the first layer 1102 may be configured to store data.As such, the first servo pattern 1114 a on the portion of second layer1104 (corresponding to the first servo pattern 1114 a in the first layer1102) may be overwritten with data.

FIG. 11C is a schematic 1100 c showing a top view of portions of aplurality of tracks configured to store servo information after a secondstep. FIG. 11D is a schematic 1100 d showing a side view of FIG. 11Cwhen viewed from the direction indicated by 1112 b in FIG. 11C. FIG. 11Cshows that the second step includes writing a second servo pattern 1116a (including addressing information) to a segment along a second track1104 a in the second layer 1104. The magnetic head may move half a trackwidth after completion of the first step to carry out writing of thesecond track 1104 a in the second step. The method may include writingthe second servo pattern 1116 a on the segment of the second track 1104a in the second layer 1104. In various embodiments, the method mayfurther include writing the second servo pattern 1120 a (includingaddressing information) on a portion of the first layer 1102, theportion of the first layer 1102 below the segment of the second track1104 a of the second layer 1104 (for writing the second servo pattern1116 a). The second servo pattern 1120 a on the portion of the firstlayer 1102 may be written together with the second servo pattern 1116 aon a segment of the second track 1104 a in the second layer 1104. Theportion of the first layer 1102 may include about half of the firsttrack 1102 a. The about half of the first track 1102 b may be directlybelow the second servo pattern 1116 a. The portion of the first layer1102 may include about half of the third track 1102 b. The about half ofthe first track 1102 b may be directly below the second servo pattern1116 a.

FIG. 11E is a schematic 1100 e showing a top view of portions of aplurality of tracks configured to store servo information after a thirdstep. FIG. 11F is a schematic 1100 f showing a side view of FIG. 11Ewhen viewed from the direction indicated by 1112 c in FIG. 11E. FIG. 11Eshows that the third step includes writing a third servo pattern 1114 b(including a subsequent servo burst) to a segment along a third track1102 b in the first layer 1102. The magnetic head may move half a trackwidth after completion of the second step to carry out writing of thethird track 1102 b in the third step. The subsequent servo burst may beof a second frequency. The third servo pattern 1114 b may also bewritten to a portion of the second layer 1104 corresponding to the thirdservo pattern 1114 b in the first layer 1102. The portion of the secondlayer 1104 corresponding to the third servo pattern 1114 b in the firstlayer 1102 may be configured to store data. As such, the third servopattern 1114 b on the portion of second layer 1104 (corresponding to thethird servo pattern 1114 b in the first layer 1102) may be overwrittenwith data.

FIG. 11G is a schematic 1100 g showing a top view of portions of aplurality of tracks configured to store servo information after a fourthstep. FIG. 11H is a schematic 1100 h showing a side view of FIG. 11Gwhen viewed from the direction indicated by 1112 d in FIG. 11G. FIG. 11Gshows that the fourth step includes writing a fourth servo pattern 1116b (including addressing information) to a segment along a fourth track1104 b in the second layer 1104. The magnetic head may move half a trackwidth after completion of the third step to carry out writing of thefourth track 1104 b in the fourth step. The method may include writingthe fourth servo pattern 1120 b (including addressing information) on aportion of the first layer 1102 corresponding the fourth servo pattern1116 b on the segment of the second track 1104 a in the second layer1104. In various embodiments, the method may further include writing thefourth servo pattern 1120 b (including addressing information) on aportion of the first layer 1102, the portion of the first layer 1102below the segment of the fourth track 1104 b of the second layer 1104(for writing the second servo pattern 1116 b). The fourth servo pattern1120 b on the portion of the first layer 1102 may be written togetherwith the fourth servo pattern 1116 b on a segment of the second track1104 a in the second layer 1104.

The method may include subsequent steps to write the subsequent servopattern including servo bursts to the servo tracks or to write thesubsequent servo pattern including addressing information to the datatracks. The steps may be repeated until the entire surface of therecording medium is written.

The first step and the second step may be carried out in a single pass.The first step, the second step, the third step, the fourth steps andthe subsequent steps may be carried out in a single pass.

The magnetic head may be a wide head.

The first servo pattern (including the servo burst pattern) on thesegment of the first track of the first layer, the second servo patternincluding addressing information on the segment of the first track ofthe first layer and the second servo pattern (including addressinginformation) on the segment of the second track of the second layer maybe formed in a single pass.

Various embodiments may include doubling the total track numbers as themagnetic head is moved half a track width for each step.

In various embodiments, the second layer (data recording layer) mayinclude disk repeatable run out (RRO) compensation information.

In various other embodiments, the first step may include writing a firstservo pattern 1114 a including a servo burst pattern to a segment alonga first track 1102 a in the first layer 1102. The second step mayinclude moving the magnetic head by one track width. The second step mayinclude writing a third servo pattern 1114 b including a subsequentservo burst pattern to a segment along a third track 1102 b. Thesubsequent steps may include moving the magnetic head by one trackwidth. The subsequent steps may include writing subsequent servopatterns including subsequent servo burst patterns until all the servoburst patterns have been written. The servo patterns including servobursts may be written by a wide head. In other words, the magnetic headmay be a wide head. The method may further include writing servoinformation 1116 a including addressing information to a segment alongthe second track 1104 a in the second layer 1102. Writing the servopattern 1116 a including the addressing information may be carried outusing a subsequent magnetic head. The method may further include movingthe subsequent magnetic head by one track width. The method may furtherinclude writing a fourth servo burst pattern 1116 b including addressinginformation to a segment along the fourth track 1104 b in the secondlayer 1104 (using the subsequent magnetic head). The method may alsoinclude writing subsequent servo patterns including addressinginformation by moving the subsequent magnetic head by one track width ata time and writing the addressing information until all the addressinginformation has been written. The subsequent magnetic head may be aproduct head.

FIG. 12 is an image 1200 showing the signal map of a multi-layerrecording medium after a writing pass is carried out according tovarious embodiments. Image 1200 shows that the addressing information1224 in the data tracks 1226 are aligned by half a track width from theservo bursts 1228 in the servo tracks 1230.

In various embodiments, a method of writing servo information may beprovided. The method may include forming a first servo pattern(including a servo burst pattern) on a segment of a first track of afirst layer of the recording medium, the first track having a trackwidth. The method may further include forming a second servo pattern(including addressing information) on a segment of a second track of asecond layer of the recording medium. The second track may be arrangedfrom the first track by half the track width.

The method may further include forming a third servo pattern (includinga subsequent servo burst pattern) on a segment of a third track of thefirst layer of the recording medium. The third track may be arrangedfrom the second track by half a track width. The second track may bebetween the first track and the third track.

In various embodiments, the servo burst pattern may be of a firstfrequency and the subsequent servo burst pattern may be of a secondfrequency. Alternatively, the servo burst pattern and the subsequentservo burst pattern may be of a single frequency. The servo burstpattern and the subsequent servo burst pattern may be of direct current(DC).

The addressing information may include auto gain control (AGC), sectoraddress mark (SAM) and GrayCode.

In various embodiments, the second layer may be over the first layer.

The method may further include forming an intermediate servo pattern(including the addressing information) on a subsequent segment of thefirst track of the first layer of the recording medium.

In various embodiments, forming the first servo pattern (including theservo burst pattern) on the segment of the first track of the firstlayer of the recording medium may be carried out during a writing passof a magnetic head. In various embodiments, forming the intermediateservo pattern (including the addressing information) on the subsequentsegment of the first track of the first layer of the recording mediummay be carried out during the same writing pass of the magnetic head. Inother words, the first servo information on the segment of the firsttrack of the first layer and the intermediate servo information on thesubsequent segment of the first track of the first layer may be formedduring a single writing pass of the magnetic head.

In various embodiments, the magnetic head may be a wide head.

In various embodiments, forming the second servo pattern (includingaddressing information) on the segment of the second track of the secondlayer of the recording medium may be carried out during a subsequentwriting pass of a subsequent magnetic head.

In various embodiments, the subsequent magnetic head may be a producthead.

In various embodiments, the intermediate servo pattern formed on thesubsequent segment of the first track of the first layer of therecording medium during the writing pass may be used as a reference whenforming the second servo pattern on the segment of the second track ofthe second layer during the subsequent writing pass.

The intermediate servo pattern formed on the subsequent segment of thefirst track of the first layer of the recording medium during thewriting pass may be distorted when forming the second servo pattern onthe segment of the second track of the second layer during thesubsequent writing pass.

In various embodiments, forming the second servo pattern (includingaddressing information) may further include forming the second servopattern (including addressing information) on a portion of the firstlayer, the portion of the first layer corresponding to the segment ofthe second track of the second layer.

In various embodiments, the second layer may be over the first layer.Forming the second servo pattern (including addressing information) mayfurther include forming the second servo pattern (including addressinginformation) on a portion the first layer, the portion of the firstlayer below the segment of the second track of the second layer. Inother words, the second servo pattern (including addressing information)may be further formed on a portion of the first layer, the portioncorresponding to (e.g. below) the segment of the second track of thesecond layer, in addition to forming the second servo pattern on thesegment of the second track of the second layer.

In various embodiments, the first servo pattern (including the servoburst pattern on the segment of the first track of the first layer, thesecond servo pattern (including addressing information) on the segmentof the first track of the first layer and the second servo pattern(including addressing information) on the segment of the second track ofthe second layer may be formed in a single writing pass.

The single writing pass may be carried out using a wide head.

In various embodiments, a recording medium may be provided. Therecording medium may include a first servo pattern (including a servoburst pattern) on a segment of a first track of a first layer of therecording medium.

The recording medium may also include second servo pattern may includeaddressing information on a segment of a second track of a second layerof the recording medium. The second track may be arranged from the firsttrack by half the track width.

In various embodiments, the recording medium may further include a thirdservo pattern (including a subsequent servo burst pattern) on a segmentof a third track of the first layer of the recording medium. The thirdtrack may be arranged from the second track by half a track width. Thesecond track may be between the first track and the third track.

In various embodiments, the servo burst pattern may be of a firstfrequency and the subsequent servo burst pattern may be of a secondfrequency. Alternatively, the servo burst pattern and the subsequentservo burst pattern may be of a single frequency. The servo burstpattern and the subsequent servo burst pattern may be of direct current(DC).

The addressing information may include auto gain control (AGC), sectoraddress mark (SAM) and GrayCode.

In various embodiments, the second layer may be over the first layer.

In various embodiments, the recording medium may further include anintermediate servo pattern (including the addressing information) on asubsequent segment of the first track of the first layer of therecording medium.

The first servo pattern (including the servo burst pattern) on thesegment of the first track of the first layer of the recording mediummay be formed during a writing pass of the magnetic head. Theintermediate servo pattern (including the addressing information) on thesubsequent segment of the first track of the first layer of therecording medium may be formed during the same writing pass of themagnetic head. In other words, the first servo information on thesegment of the first track of the first layer and the intermediate servoinformation on the subsequent segment of the first track of the firstlayer may be formed during a single writing pass of the magnetic head.

The magnetic head may be a wide head.

In various embodiments, the second servo pattern (including addressinginformation) on the segment of the second track of the second layer ofthe recording medium may be formed during a subsequent writing pass of asubsequent magnetic head. The subsequent magnetic head may be a producthead.

In various embodiments, the intermediate servo pattern on the subsequentsegment of the first track of the first layer of the recording mediumformed during the writing pass may be used as a reference for the secondservo pattern on the segment of the second track of the second layerformed during the subsequent writing pass.

In various embodiments, the intermediate servo pattern on the subsequentsegment of the first track of the first layer of the recording mediumformed during the writing pass may be distorted by the second servopattern on the second track of the second layer formed during thesubsequent writing pass.

In various embodiments, the second servo pattern (including addressinginformation) may be further include formed on a portion of the firstlayer, the portion of the first layer corresponding to the segment ofthe second track of the second layer.

In various embodiments, the second layer may be over the first layer.The second servo pattern (including addressing information) may befurther formed on a portion of the first layer, the portion of the firstlayer below the segment of the second track of the second layer. Inother words, the second servo pattern (including addressing information)may be further formed on a portion of the first layer, the portioncorresponding to (e.g. below) the segment of the second track of thesecond layer, in addition to forming the second servo pattern on thesegment of the second track of the second layer.

In various embodiments, the first servo pattern (including the servoburst pattern) on the segment of the first track of the first layer, thesecond servo pattern (including addressing information) on the segmentof the first track of the first layer and the second servo pattern(including the addressing information) on the segment of the secondtrack of the second layer may be formed in a single writing pass.

The single writing pass may be carried out using a wide head.

The data storage device may include a memory which is for example usedin the processing carried out by the data storage device. A memory usedin the embodiments may be a volatile memory, for example a DRAM (DynamicRandom Access Memory) or a non-volatile memory, for example a PROM(Programmable Read Only Memory), an EPROM (Erasable PROM), EEPROM(Electrically Erasable PROM), or a flash memory, e.g., a floating gatememory, a charge trapping memory, an MRAM (Magnetoresistive RandomAccess Memory) or a PCRAM (Phase Change Random Access Memory).

While several exemplary embodiments have been presented in the foregoingdetailed description of the invention, it should be appreciated that avast number of variations exist, including variations as to the choiceof bearings. It will be understood by one skilled in the art that wherefluid dynamic bearings are not used, the bias ring may be an optionalfeature. Also, the step of pre-assembly should be understood to beoptional as the bias ring may be embedded or otherwise provided as anintegral part of the stator, etc.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

What is claimed is:
 1. A servo system for writing servo information on arecording medium of a hard disk drive and for determining head positionbased on the servo information with a tracking accuracy, the servosystem comprising: a first magnetic head; and a servo writer configuredto write the servo information on the recording medium of the hard diskdrive by: forming, using the first magnetic head, a first servo patterncomprising a servo burst pattern on a segment of a first track of afirst layer of the recording medium of the hard disk drive; and forminga second servo pattern comprising addressing information on a segment ofa second track of a second layer of the recording medium of the harddisk drive, wherein the second track is arranged half a width of thefirst track from the first track; and wherein arranging the second trackhalf the width of the first track from the first track increases thetracking accuracy of the servo system.
 2. The servo system of claim 1,wherein the servo writer is further configured to: form a third servopattern comprising a subsequent servo burst pattern on a segment of athird track of the first layer of the recording medium, wherein thethird track is arranged from the second track by half a width of thesecond track.
 3. The servo system of claim 2, wherein the second trackis between the first track and the third track.
 4. The servo system ofclaim 2, wherein: the servo burst pattern is of a first frequency; andthe subsequent servo burst pattern is of a second frequency.
 5. Theservo system of claim 2, wherein the servo burst pattern and thesubsequent servo burst pattern is of a single frequency.
 6. The servosystem of claim 1, wherein the addressing information comprisesautomatic gain control (AGC), sector address mark (SAM), and GrayCode.7. The servo system of claim 1, wherein the second layer is arrangedover the first layer.
 8. The servo system of claim 1, wherein the servowriter is further configured to form an intermediate servo patterncomprising the addressing information on a subsequent segment of thefirst track of the first layer of the recording medium.
 9. The servosystem of claim 8, wherein the servo writer is further configured to:form the first servo pattern comprising the servo burst pattern on thesegment of the first track of the first layer of the recording mediumduring a writing pass of the first magnetic head; and form theintermediate servo pattern comprising the addressing information on thesubsequent segment of the first track of the first layer of therecording medium during the writing pass of the first magnetic head. 10.The servo system of claim 9, wherein the first magnetic head includes awide head.
 11. The servo system of claim 9, wherein the servo writer isfurther configured to form the second servo pattern comprisingaddressing information on the segment of the second track of the secondlayer of the recording medium during a subsequent writing pass of asecond magnetic head.
 12. The servo system of claim 11, wherein thesecond magnetic head includes a head other than a wide head.
 13. Theservo system of claim 11, wherein the servo writer is further configuredto use the intermediate servo pattern formed on the subsequent segmentof the first track of the first layer of the recording medium as areference during the writing pass when forming the second servo patternon the segment of the second track of the second layer during thesubsequent writing pass.
 14. The servo system of claim 11, wherein theintermediate servo pattern formed on the subsequent segment of the firsttrack of the first layer of the recording medium during the writing passis distorted when forming the second servo pattern on the segment of thesecond track of the second layer during the subsequent writing pass. 15.The servo system of claim 1, wherein the second layer is arranged overthe first layer, and wherein the servo writer is further configured toform the second servo pattern comprising addressing information on aportion of the first layer below the segment of the second track of thesecond layer.
 16. The servo system of claim 15, wherein the servo writeris further configured to form in a single writing pass, the first servopattern comprising the servo burst pattern on the segment of the firsttrack of the first layer, the second servo pattern comprising addressinginformation on the segment of the first track of the first layer, andthe second servo pattern comprising addressing information on thesegment of the second track of the second layer.
 17. The servo system ofclaim 16, wherein the servo writer is further configured to perform thesingle writing pass using the first magnetic head, and wherein the firstmagnetic head includes a wide head.